Sensing system for cut-to-length shear

ABSTRACT

A sensing system for cut-to-length shear, for providing a shear control signal for a process line of material moving at a line speed which is a function of a voltage VL, the shear control signal being used for causing actuation of the shearing mechanism. A signal VB is derived which is a function of the predetermined cut length. A signal Vi is derived which is a function of the instantaneous length of material passing the shearing mechanism. An additional voltage Delta V is derived is a function of (VL tinertia/t) where tinertia is the time required for the shearing mechanism to respond to the shear control signal, and t is the running time required for a predetermined cut length to pass through the shearing mechanism at maximum line speed. The signals VB, Vi and Delta v are received by electronic circuitry, and a shear control signal is delivered to the shearing mechanism when the algebraic relationship is satisfied VB Vi + Delta V.

United States Patent 91 Safiuddin Nov. 27, 1973 [22] Filed:

[ SENSING SYSTEM FOR CUT-TO-LENGTH SHEAR 52 US. Cl 83/293, 83/296, 83/299 [51] Int. Cl 2 3Q 25/16 [58] Field of Search 83/293-295, 285-289, 299, 296

[56] References Cited UNITED STATES PATENTS 2,692,361 10/1954 Asbury et al. 83/289 X 3,386,321 6/1968 Maxwell 83/295 3,543,624 12/1970 Richards 83/289 X 2,298,877 10/1942 Edwards et al. 83/288 X FOREIGN PATENTS OR APPLICATIONS 624,398 7/1961 Canada 83/295 V ,32 ,24 IO 2 30 a Vb 2s --V8 k STRIP 7 5 2 3 s, 4 46 3 r t f Primary ExaminerJ. M. Meister Att0rneyF. l-l. Henson et al.

[57 ABSTRACT A sensing system for cut-to-length shear, for providing a shear control signal for a process line of material moving at a line speed which is a function of a voltage V the shear control signal being used for causing actuation of the shearing mechanism. A signal V is derived which is a function of the predetermined cut length. signal V, is derived which is a function of the instantaneous length of material passing the shearing mechanism. An additional voltage AV is derived is a function of (V t /t) where tmema is the time required for the shearing mechanism to respond to the shear control signal, and t is the running time required for a predetermined cut length to pass through the shearing mechanism at maximum line speed. The signals V Vi and Av are received by electronic circuitry, and a shear control signal is delivered to the shearing mechanism when the algebraic relationship is satisfied V Vi +AV.

3 Claims, 4 Drawing Figures CR! TO SHEAR DRIVE REG.

INPUT TERMINAL 1 SENSING SYSTEM FOR CIJT-TO-LENGTH CROSS REFERENCE TO RELATED APpnrc atioN This invention relates to a sensing system for a cut-tolength shear of a moving strip of material.

2. Description of the Prior Art In the high speed processing of materials, it is arequirement that the moving strip be measured and cut to the desired length without interrupting the moving.v

process line, a signal being generated to actuate the shearing means at the required moment in time. At

present these objectives are realized through the use-of:

photoelectric detectors and sophisticated 'digital'com puters. The photoelectric devices, while inexpensive, suffer from the disadvantage that they donor provide the requisite accuracy for cutting lengths at varying line speeds. Digital computers of the high accuracy required are very expensive. The invention described herein accomplishes the dual objectives of high accuracy under varying line processing speeds, with a relatively inexpensive system.

SUMMARY OF THE INVENTION A sensing system for providing a'shear control signal rial passing through the cutting shear means. Means are I provided for deriving an additional voltage Av-which'is a function of V,, t,,,,,,.,',,,/t) where tinema is the time required for the cutting shear'means to respond to said shear control signal, and t is the running time required for said predetermined length to pass through said cutting shear means at maximum line speed. Means are arranged for receiving the signalsV Vi and AV as an input, and for delivering said shear control signal when the algebraic relationship is satisfied: V; -"Vi 1+'AV;:-

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an electrical schematic showing the sensing system for cut-to-length shear in accordance with one illustrative embodiment of the invention;

FIG. 2 is an electrical schematic showing the sensing system for cut-to-length shear in accordance with another illustrative embodiment of the invention; and

FIGS. 3 and 4 are diagrams depicting integrator output vs. time for various line speeds, for use in explaining the operation of the embodiments of FIGS. 1 and DESCRIPTION OF THE EMBODIMENTS Referring now to FIG. 1, the system in accordance connected .between the output of the amplifier and ground as shown. The wiper contact of the potentiometer 22 is connected to the input of the amplifier 18 through a resistor 24. A biasreference voltage -V,,, which may be in the order of -20 volts is connected to the input of the amplifier 18 through a resistor 26, vernier adjustment of the voltage level to the amplifier 18 may be obtained by means of resistor 28 serially connected with a potentiometer 30, the serial combination being connected between a source of negative voltage -V and ground; the wiper contact of potentiometer 30 is connected to the input, of the amplifier 18 through a resistor 32.

The line speed may be obtained by means of a tachometer generator 34. The voltage V,, generated by the-tachometer 34 is applied to the cut length measure ment means 10 and the instantaneous length measuring 12 by means of a photoelectric switch (not shown) and a relay (not shown) having a normally open contact pair 36. (In the interests of simplicity, the photoswitch and relay coils are not shown-only the contacts are identified to indicate their respective switching roles.)

The-signalV is applied to the measurement means 10 through a resistor-capacitor filter 38,40, and is applied to the instantaneous length measurement means 12 through a resistor-capacitor filter 42,44.

An operational amplifier indicated generally at 46 is operated as an integrator, and includes in its feedback path,a variable capacitor 48 shunted by a discharge resistor 50 connected in series with a pair of relay contacts 52. The gain of the integrator 46 may be adjusted by means of resistor 54 connected in series with a potentiometer 56, the series combination being connected between the output of the integrator and ground as indicated.

.The output V of cut length measurement means 10 is applied to the voltage detector means 14 through input resistor 58, while the intergrated output Vi of instantaneous length measuring, means 12 is applied to the voltage detection means 14 through resistor 60. The voltage detection means 14 comprises an amplifier 62 having inverting (I) and non-inverting (NI) inputs, a feedback resistor 64 and an output resistor 66.

The shearing signal means 16 includes a contact relay CR having normally closed contact pairs: normally closedCRl, normally open CR2, normally closed CR3, and normally open CR4. The relay CR is connected to a source of potential +V and to the collector of a NPN transistor 68. The coil of relay CR is shunted by a protective diode 70. Completing the description, the base of transistor 68 is connected to the resistor 66 and the emitter is connected to ground through a diode 72 poled as indicated with its cathode to ground.

The FIG. 2 embodiment is quite similar to that of FIG. 1. The line signal VL is not applied to cut length measurement means 10, but only to the instantaneous lengthmeasurement means 12. The integrator 46 is replaced by a proportional integrator 74 having a resistor 76 inseries with the capacitor 48. In contemplation of this invention resistor 76 is one-tenth of the ohmic value of resistor 42.

OPERATION speed of a moving strip of material can be readily determined. If the speed is uniform then after a known elapsed time interval, a finite length of material will have passed a given point. Obviously, if material is moving at ft. per sec., in 5 seconds, 50 feet will have passed a datum point. If line speed is integrated the result is a measurement of length. The output of the integrator is a function of time, so that the longer the time interval the higher the output voltage. The integrated output voltage is therefore directly related to the length of material passing during the time interval of integration. At rated or top speed each voltage level can therefore be equated to definite lengths of material.

Considering now FIG. 3, suppose that volts corresponds to 30 feet of material, i.e. steel, aluminum, etc. If the integrator builds up to voltage or 20 volts at that instant 30 feet will have passed the shearing mechanism. However, if the shearing signal is not initiated until the 20 volts level is reached then as a result of inertia and other time lags throughout the system, then, more material will have passed the shearing mechanism, andthe shear will have out too large a strip. In the practical environment of the instant invention, it has been determined that 0.3 second delay will be experienced before the shear will actually make the cut. From FIG. 3 since the time to reach 20 volts is 3 seconds at rated or top speed, if the shearing signal is initiated 0.3 second earlier, the shearing cut will take place exactly at 30 feet.

From FIG. 3 at point 78, the integrator voltage is at 18V which is the point in time when the shearing signal VL Vi at r 0 Top Speed 20 2 Hall Speed I0 I One-Third Speed 6 A A Since the proportional integrator 74 starts off at a higher voltage, it reaches the bias voltage level V B earlier in time in the order of 0.3 seconds (the response time lag). Starting with 0 volts at [=0 it would reach V 0.3 seconds too late, but with the proportional pedestal of 2, l or volt, it is enabled to reach the level of V 0.3 second earlier.

The circuitry will now be considered in greater detail. Referring to FIG. 1, the contacts CR1 are normally closed so the shear input terminal is at ground. Contacts CR2 which will enable the shear drive reference signal to be applied, are open. The mill operator at his console dials in a voltage V, corresponding to a desired cut length. As the leading edge of the material passes a reference point the photoswitch sends a signal which causes one relay to close contact pair 36 and another relay to open the contacts 52. Assume that the mill is operating at top speed ((I) in FIG. 3) and the V is 20V. The integrator 46 begins to develop a voltage The line speed signal is fed to the summing amplifier with a gain 1/ 10, along with the bias signal V The outi put Vb of the summing amplifier is the difference:

should be initiated. If the system is made to respond when the integrator output is 2 volts less than the target voltage, this will be satisfactory for rated or top speed (I), but it would be unsatisfactory for lower line speeds (II and III). As will be seen from FIG. 3, the shearing signal would be initiated at 80 for one-half speed (II) and at 82 for one-third speed (III) the slower the speed, the more deviant the cut length will be from the desired length. The teachings of this invention obviate this undesired result by proportional voltage adjustments.

In FIG. 3 which depicts the performance of the FIG. 1 embodiment, one tenth of the line speed voltage VL/lO is subtracted from the cut length voltage VB so that the system will initiate the shear signal at the proper time. For example if VL develops 20V at top speed, it will develop 10V at half speed and 6% volts at one-third speed. Accordingly, at the following speeds the proportional voltage adjustments are:

VL VL Shear Signal Initiated Vb=Vi Top Speed 20 2 l8 Half Speed I0 I I9 One-Third Speed 6 55 SS 19 56 In the embodiment of FIG. 2, the performance of which is depicted in FIG. 4, the VL/l0 adjustment is realized by using a proportional integrator 74 which provides an initial voltage output which is proportional to:

RESISTOR 1 RESISTOR 42 10 Thus depending on the line speed signal V,,, the current through these resistors will provide a proportional voltage at time t=o,

The output of the integrator is Vi. The input to the voltage detection means 14 is therefore initially some positive voltage (since Vb is larger than Vi during build up). In our assumed case VB VL/lO 18 volts. Vi builds up and finally equals l8v. As it begins to increase beyond -l8v the signal in to the voltage detection means 14 becomes negative. After inversion the positive signal to the base of transistor 68 turns it on, and collector-emitter current flows energizing the relay CR. When the relay is energized contacts CR1 open removing the ground, contacts CR2 close, and the shear drive reference signal is initiated. Contacts CR3 may be used in various circuits to fulfill various functions such as counters, lights to indicate the initiation of shear etc. CR4 is used to initiate a signal to deenergize relays causing contacts 52 to close, and 36 to open during the period to. This discharges the capacitor 48 so that the integrator 46 may be reset. With no input signal, the voltage detector means returns to a positive output shutting off the transistor 68 deenergizing the relay CR and returning the contacts CR1, CR2, CR3, and CR4 to their state as shown in FIG. I.

The operation of the FIG. 2 embodiment is quite similar except that the use of the proportional integrator 74 produces an initial output pedestal level. Starting then at a higher voltage level, the signal v builds up faster. Now Vb=VB, and in our illustrative case Vi would build up until equated to 20 volts. As it increased beyond -20v, the system would be actuated as before.

I claim:

I. A system for providing a shear control signal for a process line of material moving at a line speed which is a function of a voltage V,,, said shear control signal actuating shear means for cutting predetermined lengths of material comprising means for deriving a voltage V, which is a function of said predetermined length;

means for integrating, arranged for receiving said voltage V and for delivering an integrated output Vi; and

means arranged for receiving said voltages Vb and Vi for algebraically adding said voltages and for delivering said shear control signal when Vb Vi.

3. A system for providing a shear control signal for required for said predetermined length to pass through the cutting shear means atmaximum line speed; and

means for receiving and algebraically adding said siga process line of material moving at a line speed which is a function of a voltage V said shear control signal 10 actuating cutting shear means for cutting predetermined lengths of material comprising:

nals VB, Vi and AV as an input and for delivering said shear control signal when the algebraic relationship is satisfied: VB Vi AV.

means for deriving a voltage VB which is a function of said predetermined cut length; means for deriving said voltage V,

means for proportionally integrating, for receiving said voltage V, and for delivering an output Av Vi, where Av is the proportionality signal of said portion integrating means and is a function of (V t /t), where t is the time required for the 2. A system for providing a shear control signal for a process line of material moving at a line speed which is a function of a voltage V said shear control signal actuating cutting shear means for cutting predetermined lenths of material comprising:

means for deriving a voltage V which is a function cutting shears to respond to said shear cutting sigof said predetermined length; nal, t is the running time required for said predetermeans for deriving said voltage V mined length to pass through the cutting shear means for amplifying connected to algebraically sum, means at maximum speed, and Vi is the integrated said voltages V V, having a less than unity gain signal portion of said porportionally integrating G numerically equal to the fraction t /t, where means; and t is the time required for the cutting shear means for receiving and algebraically adding said sigmeans to respond to said shear control signal, and nals VB and Av Vi, and for delivering said shear t is the running time required for said predetercontrol signal when: mined length to pass through the cutting shear I means at maximum line speed, said amplifier VB means delivering an output Vb equal to V GV 

1. A system for providing a shear control signal for a process line of material moving at a line speed which is a function of a voltage VL, said shear control signal actuating shear means for cutting predetermined lengths of material comprising means for deriving a voltage VB which is a function of said predetermined length; means for deriving a voltage Vi which is a function of the instantaneous length of material passing through said cutting shear means; means for deriving an additional voltage Delta V which in a function of (VL tinertia/t) where tinertia is the time required for the cutting shears means to respond to said shear control signal, and t is the running time required for said predetermined length to pass through the cutting shear means at maximum line speed; and means for receiving and algebraically adding said signals VB, Vi and Delta V as an input and for delivering said shear control signal when the algebraic relaTionship is satisfied: VB Vi + Delta V.
 2. A system for providing a shear control signal for a process line of material moving at a line speed which is a function of a voltage VL, said shear control signal actuating cutting shear means for cutting predetermined lenths of material comprising: means for deriving a voltage VB which is a function of said predetermined length; means for deriving said voltage VL; means for amplifying connected to algebraically sum, said voltages VB, VL, having a less than unity gain G numerically equal to the fraction tinertia/t, where tinertia is the time required for the cutting shear means to respond to said shear control signal, and t is the running time required for said predetermined length to pass through the cutting shear means at maximum line speed, said amplifier means delivering an output Vb equal to VB - GVL; means for integrating, arranged for receiving said voltage VL and for delivering an integrated output Vi; and means arranged for receiving said voltages Vb and Vi for algebraically adding said voltages and for delivering said shear control signal when Vb Vi.
 3. A system for providing a shear control signal for a process line of material moving at a line speed which is a function of a voltage VL, said shear control signal actuating cutting shear means for cutting predetermined lengths of material comprising: means for deriving a voltage VB which is a function of said predetermined cut length; means for deriving said voltage VL; means for proportionally integrating, for receiving said voltage VL and for delivering an output Delta v + Vi, where Delta v is the proportionality signal of said portion integrating means and is a function of (VL tinertia/t), where tinertia is the time required for the cutting shears to respond to said shear cutting signal, t is the running time required for said predetermined length to pass through the cutting shear means at maximum speed, and Vi is the integrated signal portion of said porportionally integrating means; and means for receiving and algebraically adding said signals VB and Delta v + Vi, and for delivering said shear control signal when: VB Vi + Delta V. 